Abstract DP388: National trends in regionalization of care for stroke and endovascular thrombectomy care: 2010 to 2019

Background: Patients with acute ischemic stroke (AIS) frequently require interhospital transfer to access a higher level of resources, including endovascular thrombectomy (EVT). Our objective is to describe national trends in transfer of AIS patients over time, including transfer to EVT-capable hospitals and high-volume EVT hospitals. Methods: We use traditional Medicare claims data to identify patients with AIS hospitalizations, using a study period from 2010-2019 (given the impact of the COVID-19 pandemic on transfer and care delivery patterns in 2020). We defined EVT-capability as a hospital that performs at least 2 EVTs in a given year. We defined a high-volume EVT hospital as a hospital that performed at least 10 EVTs per year, based on an analysis of the distribution of EVT procedures for each year of the study period. We categorized hospitals by year based on their EVT-capability and volume, and we calculated the proportion of patient transfers overall, and to EVT-capable and high-volume EVT hospitals by year. We used linear regression to examine trends in transfer rates over time. Results: We identified an average of 265,481 AIS encounters per year from 4,616 hospitals between 2010 to 2019, with an average of 12,304 (4.6%) transferred between hospitals per year. The proportion of hospitals with EVT capability and the proportion high-volume EVT hospitals increased over time (EVT capability: 4.8% in 2010 to 14.4% in 2019, p-value for trend < 0.001; high-volume EVT hospitals 0.9% in 2010 to 6.9% in 2019, p-value for trend < 0.001; Figure). The overall proportion of encounters transferred increased from 3.1% in 2010 to 6.0% in 2019 (p-value for trend < 0.001), the proportion of encounters transferred to EVT-capable hospitals increased from 1.4% in 2010 to 5.0% in 2019 (p-value for trend < 0.001), and the proportion of encounters transferred to high-volume EVT hospitals increased from 0.6% in 2010 to 4.0% in 2019 (p-value for trend < 0.001; Figure). Conclusions: AIS care has become increasingly regionalized from 2010-2019. As more hospitals have acquired EVT-capability, an increasing proportion of interhospital transfers are to EVT-capable hospitals. However, given known volume-outcome relationships in EVT, further work is needed to examine whether AIS regionalization patterns are optimized for patient outcomes.